The present invention is related to the field of laser amplifiers and sources for fiberoptic networks and, more particularly, to lasing elements created in a doped optical fiber.
One of the devices which has recently enhanced the use of fiberoptic networks has been the erbium-doped fiber amplifier. In the erbium-doped fiber amplifier, the light at one wavelength from a pumping laser is combined in a section of erbium-doped optical fiber with the message signal at a second wavelength. The pumping laser provides the energy for a gain in the message signal as it passes through the erbium-doped optical fiber section. The erbium-doped fiber amplifier is compatible with a fiberoptic network since the amplifier is mostly optical fiber.
On the other hand, light sources for fiberoptic networks have heretofore been mostly semiconductor devices, such as laser diodes, light-emitting diodes, and other semiconductor laser sources. A new type of laser source is a rare-earth doped optical fiber section with wavelength-selective reflectors at the ends of the section to define a lasing cavity. As in the case of the erbium-doped fiber amplifier, a pumping laser supplies energy to the doped fiber section at one, or multiple, wavelengths. The fiber section lases at one, or multiple, different output wavelengths. While seemingly compatible with fiberoptic networks, this laser source has a relatively low output power and the advantages of this laser source have yet to be appreciated.
In many fiberoptic networks, WDM (Wavelength Division Multiplexed) networks, in particular, a large number of laser sources for signal generation are required. Since the wavelength of an optical signal is used to direct the signal from its source to its destination, each user typically has a laser source operating at a specific wavelength which could be different from those of other laser sources. A laser source having a fixed and precise output wavelength is very desirable. An emerging standard is the Dense WDM proposed by the ITU, the International Telecommunications Union, in which the separation between communication channels in only 0.8 nm in wavelength, or 100 GHz in frequency. Thus the constraints for a light source with a very narrow output linewidth, i.e., the wavelength of the output signal, are even tighter.
The present invention allows for the full exploitation of the compatibility of these fiber amplifier and lasers mentioned above with fiberoptic networks. With the present invention, the output power of the fiber amplifier and lasers is increased so that the performance of fiberoptic networks using these devices is increased. Laser sources with high output power and the precise output wavelengths are presented to meet the requirements of WDM and dense WDM networks. Furthermore, the output power of fiber amplifiers is increased so that the applicability of these devices in fiberoptic networks is enhanced.